My top tip for database programming is don't do it until you absolutely have to. Hopefully by then you'll have a good idea of the 'shape' of your data and you'll end up with a reasonably stable database Schema.

Despite what gmax says about not being afraid of writing raw SQL and using DBI directly I'd still say that you should try and route all your database access through one or two modules (either tools from CPAN, or home rolled) as a way of limiting your dependencies and avoiding the problem of a single change in the database leading to the Death of a thousand cuts as you trawl your codebase hunting down everything that deals with the affected tables.

The 'performance hit' you'll see as a result of doing this will be nothing compared to increase in 'cost of change' you see when scatter SQL throughout your code like an incontinent puppy. (Guess who's had to work with code like that recently. It's painful.) And then there's testability. When you access the database only through your 'mediator' modules, it becomes possible to drop in a replacement that only pretends to talk to a 'real' database. This can be a remarkably powerful testing technique...